Ahhh the fun begins....
Hempy pots are just plain 'ol solid pots with a small hole drilled in it about 2" (ish...) up from the bottom of the pot. This forms a reservoir at the bottom of the pot. The res at the bottom provides a source of nutrients. When the vegging plant's roots hit the res, their rate of growth really bumps up and from there on, you see speeds on a par with active hydroponic systems.
There are no pumps or exterior reservoirs involved. When you feed, you flush out the remaining fluid at the bottom of the bucket and the reservoir is renewed with a fresh nutrient mix. Between waterings, the perlite (or other neutral medium) wicks water up from the reservoir and keeps the entire area of the medium lightly wet, thus providing nutrients thru the mix.
I feed and water together every 3 days. There are many configurations that have worked for many different people growing in many different environments. Some feed and water together. Some feed once a week and water between. If you use larger pots, you can get away with less waterings, but you'll go thru more water/food for each watering/feeding.
What is drain to waste, and how is that different than just runoff into a "saucer"? (In my case, the lids of the bins I plant in)
It isn't. I dump water in the top... it runs out the hole into saucers that the bucket is sitting in. When the runoff stops, I dump out the saucers. I bet you do exactly the same.
The pots will be somewhat lighter. Folks seem to be able to get away with smaller pots... and the medium is lighter than soil.
I grow in pure perlite. It just doesn't support any bug growth, and I just have not seen any bugs in a very long time. None. I did see a frog one day.... really made me wonder how he got in. Wet soil is a great environment for every bug in the world... especially as a nursery for their young. Hell... it's what Mother Nature provides... of course they thrive in it. Perlite... mostly dry at the very top.... not such an attractive environment for them.
I often say, and I'll utter the words again.... Hempy is more like soil than it is like hydro, except for the results.